1. Field of the Invention
The present invention relates to an optical fiber wavelength converter which uses a highly nonlinear optical fiber.
2. Description of the Related Art
In recent years, the communication is required to have fast processing, large capacity, and long transmission distance, therefore light signal processing technologies to enable fast processing of light signals and a long transmission distance are desired.
One approach of light signal processing is the all-optical signal processing technology in which light signals are processed as it is. Since this all-optical signal processing technology handles light signals as it is without a conversion of light signals to electric signals, a fast light signal processing is enabled.
As the all-optical signal processing technologies, for example, a method which uses nonlinear optical phenomena that occur in an optical fiber where light signals transmit, and a method which uses nonlinear phenomena that occur in an optical waveguide made of highly nonlinear substance, are known.
The former all-optical signal processing technology which uses nonlinear optical phenomena that occur in an optical fiber especially receives attentions in recent years, since it allows a fast processing as well as a low transmission loss. The nonlinear optical phenomena that occur in the optical fiber include, for example, four-wave mixing, self-phase modulation, cross-phase modulation, and Brillouin Scattering. As the light signal processing technologies, wavelength conversion using the four-wave mixing, pulse compression or Reshaping using the self-phase modulation, and the like have been proposed.
Incidentally, four-wave mixing is a phenomenon that light of different wavelength appear by nonlinear phenomena according to a specific law when light of two or more wavelengths are introduced into an optical fiber. In the all-optical signal processing technologies, this phenomenon, which allows a generation of the light of different wavelength, is used for a wavelength conversion. Moreover, the wavelength conversion using four-wave mixing has advantages of converting a multi-wavelength signal in one batch processing at a high speed and in low noise. Therefore, such technologies are important for constructing a future fast signal processing system.
Incidentally, to apply a light signal processing technology, such as wavelength conversion, an optical fiber which performs highly nonlinear phenomena, i.e. an optical fiber which has high nonlinearity is necessary(hereinafter simply referred to as “highly nonlinear optical fiber.”)
This highly nonlinear optical fiber and an optical fiber wavelength converter using the highly nonlinear optical fiber is disclosed in Japanese patent Application Laid-open No. 2001-75136.
According to the optical fiber wavelength converter disclosed in Japanese patent Application Laid-open No. 2001-75136 as well as the other optical fiber wavelength converters using such a highly nonlinear optical fiber, it is found that changes in temperature around the optical fiber wavelength converter (hereinafter, simply referred to as “environmental temperature”) change the characteristics, in particular bandwidth of the wavelength conversion. More specifically, several highly nonlinear optical fibers are manufactured, when the optical fiber wavelength converters using those fibers are operated under different environmental temperatures, the bandwidth of the wavelength conversion is changed according to the environmental temperature.